The subject matter disclosed herein relates generally to systems and methods for array focusing, and more particularly to systems including beacons for coherent beam aiming.
It has long been the goal of sensor, jamming and communications systems to find practical methods to focus, or coherently combine signals coming from or directed to an array of spatially distributed transceivers where there is imprecise knowledge of either coordinates or mutual ranges. Some examples of such arrays of arbitrarily placed nodes may include communication or guidance systems, such as satellite systems, aircraft radar systems or hand-held radio systems. The wavelengths in these systems are either small relative to the separation of the transceivers or the system dynamics make it impractical to have transceivers cooperatively focus energy based on the instantaneous knowledge of relative position and timing. Even for a precisely surveyed phased array that is large physically when compared to the wavelength, the mechanical vibration of the structure may induce sufficient relative motion among the array elements to destroy coherence.
Thus, conventional systems are using retrodirectivity to cohere an array with a beacon that requires close placement of the beacon near the target area. In these systems, retrodirectivity is used to cohere the array by a reference beacon that is placed near the target and then by perturbing the transmit phases to steer the beam to a target slightly away from beacon. Since in retrodirectivity the beacon operates at the same frequency as the array, a passive reflector at or near the target location can also act as the phase reference.